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* ioext.c (scm_read_string_x_partial): new procedure, implements

Browse source 
read-string!/partial.
	* ports.c (scm_take_from_input_buffers): new procedure used by
	scm_read_string_x_partial.
	(scm_drain_input): use scm_take_from_input_buffers.
This commit is contained in:
Gary Houston 2001-01-06 22:03:07 +00:00
parent 4651d663fa
commit c2da26487a
6 changed files with 151 additions and 15 deletions
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104
libguile/ioext.c
View file

@ -69,6 +69,110 @@
#endif
SCM_DEFINE (scm_read_string_x_partial, "read-string!/partial", 1, 3, 0,
(SCM str, SCM port_or_fdes, SCM start, SCM end),
"Read characters from an fport or file descriptor into a\n"
"string @var{str}. This procedure is scsh-compatible\n"
"and can efficiently read large strings. It will:\n\n"
"@itemize\n"
"@item\n"
"attempt to fill the entire string, unless the @var{start}\n"
"and/or @var{end} arguments are supplied. i.e., @var{start}\n"
"defaults to 0 and @var{end} defaults to\n"
"@code{(string-length str)}\n"
"@item\n"
"use the current input port if @var{port_or_fdes} is not\n"
"supplied.\n"
"@item\n"
"read any characters that are currently available,\n"
"without waiting for the rest (short reads are possible).\n\n"
"@item\n"
"wait for as long as it needs to for the first character to\n"
"become available, unless the port is in non-blocking mode\n"
"@item\n"
"return @code{#f} if end-of-file is encountered before reading\n"
"any characters, otherwise return the number of characters\n"
"read.\n"
"@item\n"
"return 0 if the port is in non-blocking mode and no characters\n"
"are immediately available.\n"
"@item\n"
"return 0 if the request is for 0 bytes, with no\n"
"end-of-file check\n"
"@end itemize")
#define FUNC_NAME s_scm_read_string_x_partial
{
char *dest;
long read_len;
long chars_read = 0;
int fdes = -1;
SCM port = SCM_BOOL_F;
SCM_VALIDATE_STRING_COPY (1, str, dest);
if (SCM_UNBNDP (port_or_fdes))
port = scm_cur_inp;
else if (SCM_INUMP (port_or_fdes))
fdes = SCM_INUM (port_or_fdes);
else
{
SCM_VALIDATE_OPFPORT (2, port_or_fdes);
SCM_VALIDATE_INPUT_PORT (2, port_or_fdes);
port = port_or_fdes;
}
{
long string_len = SCM_STRING_LENGTH (str);
long offset = SCM_NUM2LONG_DEF (3, start, 0);
long last = SCM_NUM2LONG_DEF (4, end, string_len);
if (offset < 0 || offset > string_len)
SCM_OUT_OF_RANGE (3, start);
if (last < offset || last > string_len)
SCM_OUT_OF_RANGE (4, end);
dest += offset;
read_len = last - offset;
}
if (fdes == -1)
{
/* if there's anything in the port buffers, use it. but if
something is read from the buffers, don't touch the file
descriptor. otherwise the "return immediately if something
is available" rule may be violated. */
chars_read = scm_take_from_input_buffers (port, dest, read_len);
}
if (chars_read == 0 && read_len > 0) /* don't confuse read_len == 0 with
EOF. */
{
if (fdes == -1)
fdes = SCM_FPORT_FDES (port);
SCM_SYSCALL (chars_read = read (fdes, dest, read_len));
if (chars_read == -1)
{
#if defined (EWOULDBLOCK) || defined (EAGAIN)
if (
#if defined (EWOULDBLOCK)
errno == EWOULDBLOCK
#else
errno == EAGAIN
#endif
)
chars_read = 0;
else
#endif
SCM_SYSERROR;
}
else if (chars_read == 0)
return SCM_BOOL_F;
}
return scm_long2num (chars_read);
}
#undef FUNC_NAME
SCM_DEFINE (scm_read_delimited_x, "%read-delimited!", 3, 3, 0,
(SCM delims, SCM buf, SCM gobble, SCM port, SCM start, SCM end),
"Read characters from @var{port} into @var{buf} until one of the\n"